Gas turbine engines are commonly used to generate energy and propulsion in many modern aircraft as well as other vehicles and industrial processes. Many such engines include a fan, compressor, combustor and turbine provided in serial fashion, forming an engine core and arranged along a central longitudinal axis. Air enters the gas turbine engine through the fan and is pressurized in the compressor. This pressurized air is mixed with fuel in the combustor. The fuel-air mixture is then ignited, generating hot combustion gases that flow downstream to the turbine. The turbine is driven by the exhaust gases and mechanically powers the compressor and fan via a central rotating shaft. Energy from the combustion gases not used by the turbine is discharged through an exhaust nozzle, producing thrust to power the aircraft.
In light of this it can be seen that the airfoils of a gas turbine engine, in addition to the fan, compressor, and turbine blades and vanes, are subjected to extreme internal temperatures and weather conditions when the gas turbine engine is in operation. Accordingly, such airfoils need to be manufactured well. Many issues can occur with the airfoils which can lead to dangerous or less than optimal operation of the gas turbine engine. One of these situations occurs when electrostatic charge builds up on the airfoils of the gas turbine engine.
When the gas turbine engine is in operation, the airfoils of the fan rotate around a central longitudinal axis providing thrust for the engine. However, the air that passes through these airfoils providing the thrust needed from propulsion is not free from impurities. In operating conditions the air that passes through the gas turbine engine may have snow, dust, sand, or volcanic ash particles along with it as it passes through the gas turbine engine. Even though these particles are non-conductive materials, when these particles pass by the airfoils of the gas turbine engine they can rub against the airfoils causing electrostatic charging on the airfoils. The friction of the impurity particles against the airfoils causes this buildup of electrostatic charge.
Electrostatic charge build up on the airfoils of a gas turbine engine can lead to dangerous outcomes. If the electrostatic charge is not properly dissipated, the electrostatic charge can spark and cause injury to ground workers approaching the gas turbine engine after operation. The electrostatic charge build up on the airfoils can also spark from the airfoils to the sides of the gas turbine engine enclosure or other airfoils leading to possible material or surface damage to these components. In catastrophic operational scenarios, it is possible that this electrostatic charge build up could spark and improperly ignite fuel vapors outside the gas turbine engine environment. Additionally, electrostatic charge buildup and sparking can lead to radio interference for the pilot hindering communication with other aircraft or flight control.
Even if the electrostatic charge build up on the airfoils does not discharge as a spark, the buildup of static charge can still limit optimal operation of the gas turbine engine. If the electrostatic charge buildup does not spark, electronic charge will accumulate on the airfoils eventually ionize the air surrounding the airfoils. This effect is called a corona. The presence of a corona around the airfoils can lead to increased radio interference and make radio communication difficult for the pilot.
Therefore, it would be advantageous to produce an airfoil of sufficient strength and design to avoid the buildup of electrostatic charge. Furthermore, is would be advantageous for the airfoil to properly dissipate the buildup of electrostatic charge so that proper operation of the gas turbine engine can be achieved without the unnecessary and potential dangerous consequences the buildup of electrostatic charge on the airfoil presents.